Source-Water Chemistry — Alkalinity, Sodium & the Numbers Under the EC
Why EC alone hides the two water problems that wreck a program — bicarbonate alkalinity and sodium/chloride — plus the acid-to-alkalinity math and the RO-blend decision, all brand-agnostic.
The water-room lesson told you to test source water for EC, pH, alkalinity, and Na/Cl. This lesson is the deep dive on why the last two matter more than the first two — and why a grower who only checks EC and pH is flying half-blind. EC tells you how much dissolved salt is present; it says nothing about which salts. Two waters can read an identical 0.4 mS/cm: one is harmless dissolved calcium and magnesium your plant wants, the other is sodium bicarbonate that will drive your root-zone pH up and stack sodium toward toxicity. Same EC, opposite outcomes.
pH is a snapshot of acidity right now; alkalinity is the water's buffering capacity — its resistance to pH change, driven mostly by bicarbonate (HCO₃⁻) and carbonate. A water can read a friendly pH 7.0 and still carry crushing alkalinity. That bicarbonate is a base reservoir: every irrigation it neutralizes your pH-down and slowly pushes root-zone pH upward toward the >6.5 zone where Fe/Mn/Zn/B lock out. This is why growers who 'pH their water to 6.0' still drift into micro lockout over weeks — they corrected the pH but never neutralized the alkalinity behind it. Measure alkalinity (as mg/L CaCO₃), not just pH.
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